A phacoemulsification surgical instrument provides for the breaking apart and the removal of unwanted tissue and material, especially a cataract located in the capsular bag or sac of the eye, by ultrasonically fragmenting the cataract while simultaneously introducing fluid into the eye and withdrawing the fluid and fragmented cataract particles from the eye. A typical phacoemulsification instrument includes a handpiece having an operative needle vibrating in the ultrasonic range. The needle shaft is hollow and is, in turn, surrounded by a tubular sleeve. In operation, the needle shaft, including the surrounding tubular sleeve, is inserted through the anterior chamber of the eye and into the capsular bag. Irrigation fluid is introduced through the hollow sleeve to provide a replacement for fluid withdrawn or lost from the eye chamber during surgery. The needle tip is used to emulsify the cataract. The fluid and fragmented or emulsified cataract are removed from the eye through the hollow needle via a suction source provided through the handpiece.
The capsular bag or sac contains a gel-like lens nucleus which acts to focus light rays entering the eye onto the retina to produce sight. A cataract is a clouting or growth within the gel-like material of the capsular sac. It is desirable to emulsify the lens nucleus in situ because removing the nucleus from its original position and emulsifying the nucleus elsewhere in the eye creates a possibility of damage to other eye tissue, such as damage to the iris and/or corneal endothelium. However, emulsification of the lens nucleus in situ causes additional problems, particularly the danger of rupturing the back of, or the posterior portion, of capsular sac. If the posterior capsular sac surface encounters a sharp instrument, such as a sharpened vibrating needle, or too great a suction is created within the hollow needle, the posterior surface of the capsular bag may be punctured, and once its structural integrity is broken, the capsular bag generally splits and tears.
Danger to the posterior surface of the capsular bag results in the loss of vitreous humor and lens particles and other material falling into the posterior chamber of the eye resulting in undesirable complications, dangers and difficulties in performing cataract surgery and patient recovery. In most cataract operations, once the lens nucleus is removed from the eye, an intraocular lens (IOL) is positioned within the capsular sac. However, if the structural integrity of the capsular sac has been destroyed by piercing or undo vacuum pressures, then the IOL cannot be properly positioned and held within the capsular sac. At this point, a physician's options are limited thus the physician would be required to use an IOL which is affixed within the anterior chamber of the eye. This is often not the optimal placement for an IOL.
A needle has thus arisen for a phacoemulsification needle having a tip which greatly reduces the probability of damaging the integrity of the capsular sac either through piercing or the creation of too much negative pressure.